Opening up baryon-number-violating operators

Abstract

Baryon number violation is our most sensitive probe of physics beyond the Standard Model. Its realization through heavy new particles can be conveniently encoded in higher-dimensional operators that allow for model-agnostic analyses. The unparalleled sensitivity of nuclear decays to baryon number violation makes it possible to probe effective operators of very high mass dimension, far beyond the commonly discussed dimension-six operators. To facilitate studies of this ginormous and scarcely explored testable operator landscape we provide the exhaustive set of tree-level UV completions consisting of scalars, fermions, and vectors for non-derivative baryon-number-violating operators in this Standard Model effective field theory up to mass dimension 15, which corresponds roughly to the border of sensitivity. In addition to the known Standard Model fields we also include right-handed neutrinos in our operators. Our public code can be used to UV-complete any non-derivative operator and match it onto an operator basis.

Figures (14)

• Figure 1: Feynman-diagram topology for the $d=6$ operators from Eq. \ref{['eq:dequal6basis_simple']}, involving four external SM fermions (solid black lines) and one new heavy boson (dashed red line).
• Figure 5: Feynman diagrams involving gauge-singlet particles that UV-complete the operator $\mathcal{O}^{3}_{7,(1,-1)}=\bar{H}ddu\bar{L}$ (left) and $\mathcal{O}^{10}_{12,(2,2)} = uuuuddee$ (right), with all momenta incoming.
• Figure 6: Example UV completion for the $d=15$ operator $\mathcal{O}_{15, \,(1 , 7)}^{11} \equiv u u d e \nu \nu \nu \nu \nu \nu$ that leads to $p\to e^+\bar{\nu}\bar{\nu}\bar{\nu}\bar{\nu}\bar{\nu}\bar{\nu}$ with heavy scalars $S_2 \sim ({\boldsymbol{3}},{\boldsymbol{1}},-1/3)$ and $S_7 \sim ({\boldsymbol{1}},{\boldsymbol{1}},0)$.
• Figure 7: Feynman-diagram topologies for the $d=7$, $\Delta B = 1$ operators, involving four external SM fermions (solid black lines), one external scalar (dashed black) and new heavy fermions (red) or bosons (dashed red).
• Figure 8: Feynman-diagram topologies for $d=8$ BNV operators.